Influence of feed concentration and pH on iron and manganese rejection via nanohybrid polysulfone/Ag-GO ultrafiltration membrane

ABSTRACT Iron and manganese are elements that exist naturally in water, especially groundwater. The aim of this work is to study the rejection mechanisms of iron and manganese at various feed concentration and investigate the influence of pH on metallic ions rejection using fabricated polysulfone (PSF) incorporated with silver-decorated graphene oxide (Ag-GO) ultrafiltration (UF) membrane or designated as GOS UF membrane. In single electrolyte solutions with feed concentration at 100 ppm and initial pH of 5.9 ± 0.3, the rejection of iron and manganese were ≥83% and ≥60% respectively. Higher rejection was achieved as feed concentration increased to 1000 ppm for each ion with rejection of iron was ≥90% and manganese ≥75%. However, iron rejection was slightly decreased to ~78%, while manganese rejection severely declined to ~22% in multi-electrolytes filtration with feed concentration of 100 ppm iron and 50 ppm manganese. The feed pH for multi component system has significantly influenced iron and manganese rejection due to changes of the membrane surface properties. The rejection of iron and manganese by the negatively charged GOS UF membrane varied from 76% to 99% by adjustment of pH in the range of 3 to 11. Manganese rejection is mostly pH dependent with ≥97% rejection at feed pH ≥9. This mixed matrix membrane with superior properties has the potential to remove iron and manganese to the desired extent for groundwater treatment.